The alignment network has a temporal receptive field of three seconds at 25 FPS, i.e., 75 frames. Each frame is represented by a tensor of size \(5\times 120\times 120\) , where the five channels correspond to the five consecutive frames above. This redundant representation, in which the same cropped mouth frames appear in multiple tensors, follows the early fusion model suggested by Chung and Zisserman [1]}.
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